1. Field of the Invention
The present invention relates to a bearing device, and a conveying device, an inspection device, and a machine tool using the bearing device.
2. Description of the Related Art
Direct drive motors (bearing devices, hereinafter referred to as DD motors) that employ a drive system (motor load direct connection type drive system) to directly transmit rotational force to a rotating body, and rotate the rotating body in a predetermined direction with respect to a rotated body are conventionally known. This kind of DD motor includes a bearing including an inner ring and an outer ring arranged to face each other with a rolling element interposed therebetween, a first housing supported by the inner ring, and a second housing supported by the outer ring, and rotates the first housing or the second housing as an output shaft (rotating body). The DD motor detects a rotational state (for example, a rotational speed, a rotating direction, and a rotation angle) of the output shaft in a more accurate manner in order to position the output shaft while rotating the output shaft in a highly accurate manner. Therefore, the support structure of the bearing to support the housings is important, and especially, suppression of movement (thrust play) of the bearing in the axial direction is required. Conventionally, C-type retaining rings have been often used to fix the bearing in the axial direction of the bearing. In this technology, a groove with a diameter slightly larger than an outer diameter of the bearing is machined in one of the housings (for example, the second housing) near the bearing, and a C-type retaining ring is mounted in the groove, so that the bearing is fixed in the axial direction using force of the retaining ring expanding outward. However, in this technology, machining errors of the groove and the like need to be taken into account in addition to dimensional tolerance of the bearing and the C-type retaining ring in the axial direction, and complete suppression of the movement of the bearing in the axial direction is difficult.
To realize highly accurate rotation of the motor while suppressing the movement of the bearing in the axial direction, and firmly support the load fixed to the output shaft, in a conventionally proposed structure, the first housing and the second housing are each divided into two parts at bearing portions in the axial direction such that the divided housings sandwich the bearing, and the divided housings are fastened with bolts or the like (for example, see Prior Art 1).
Prior Art 1: JP 4636432 B2
By the way, as a product for industrial application, it is important to configure the bearing incorporable as easily as possible, and downsize the bearing. In the conventional technology, the movement of the bearing in the axial direction can be suppressed, but the support structure of the bearing is complicated. Furthermore, in a case where the divided housings are fastened with bolts, a plurality of bolts (for example, six bolts or more) is typically provided on a concentric circle with the bearing. The plurality of bolts needs to be uniformly fastened so that the housings are uniformly in contact with an end surface of the bearing in the axial direction. Although it is possible for a human to tighten the bolts little by little while feeling contact reaction force against screw holes, it takes long to perform the work, and it has been difficult to automate the work using a device.
The present invention solves the above-described problem, and an objective is to provide a bearing device that can prevent movement of a bearing in an axial direction with a simple configuration, and a conveying device, an inspection device, and a machine tool that use the bearing device.